Using a dye dilutiion technique combined with rapid sampling, gastric emptying and secretion are being evaluated in vivo in man, dogs, and monkeys. Results obtained from such studies are being used to develop a mathematical model of gastric emptying and to explore the role played by gastric emptying in various clinical disorders such as postoperative ileus, Zollinger-Ellison syndrome, and duodenal ulcer. BIBLIOGRAPHIC REFERENCES: Dubois, A., Van Eerdewegh, P., Line, B., Van Maele, P., and Gardner, J. D.: A new method for simultaneous determination of gastric emptying and secretion. Proc. 5th Int. Symp. on Gastrointestinal Motility, Van Trappen, Ed., Leuven, 1977, pp. 244-247. Dubois, A., Van Eerdewegh, P., and Gardner, J. D.: Gastric emptying and secretion in Zollinger-Ellison Syndrome. J. Clin. Invest. 59:255-263, 1977.